As is well known, solid carbonaeous materials, e.g., wood and coal can be liquefied by controlled heating in the absence of oxygen to obtain a liquid, gas and char. Such technology is of especially important consideration in view of the depletion of the world's petroleum reserves and represents a plausible route for utilization of such carbonaceous material resources to complement and enhance conventional petroleum fuels and chemical products derived from petroleum. Naturally, the conversion of such materials into liquid form, especially as a fuel, is extremely desirable because of the ease of handling in various petroleum-treatment processes, and more particularly to permit use along with conventional liquid petroleum products in current energy utilization technology which is adapted to handle liquid sources of energy.
Thus, due to the compelling factors of economy and conservation, the technology of coal liquefaction has been growing considerably. The production of oil by the destructive distillation of wood has also been receiving increased attention.
The conversion of cellulose and/or wood to a hydrocarbon-like product requires the removal of combined oxygen. Rejection of oxygen in the form of water would not lead to the formation of hydrocarbons unless external hydrogen is added. Rejection of oxygen by the formation of CO.sub.2, on the other hand, could, in theory, enrich wood in hydrogen without the addition of any external hydrogen. Thus, the decarboxylation of wood represents a desirable process for the upgrading of wood from a carbohydrate rich solid to a petroleum-like liquid. The degree of upgrading may be measured by the effective hydrogen concentration of the product. This effective hydrogen index is defined in terms of atomic ratios as follows: ##EQU1## where H, C, O, N, S are the number of atoms per formula weight of sample of hydrogen, carbon, oxygen, nitrogen and sulfur, respectively, as determined by elemental analysis.
Thus, for example, cellulose (C.sub.6 H.sub.10 O.sub.5).sub.n, the main building block of wood, being a carbohydrate, has an effective hydrogen index of zero; the rejection of O.sub.2 as water leads to carbon and not hydrocarbon.
U.S. Pat. No. 4,052,292 is representative of most recent technology and decribes the conversion of carbonaceous materials into liquid products by heating slurries of these materials in aromatic solvents at elevated temperatures. While the process described in the said patent is quite effective in converting said materials into liquid products, the product still contains a significant amount of combined oxygen and a relatively low effective hydrogen index.
Thus, there remains the need for improvement of the procedures for converting carbonaceous materials to liquefied products of higher effective hydrogen index and lower combined oxygen content.
The present invention provides an improved method for converting carbonaceous materials into liquid products having application as fuels and chemical derivatives. More specifically, the present invention provides a process to solubilize carbonaceous materials in an aromatic petroleum or coal-derived solvent to yield a product of improved effective hydrogen index, particularly in comparison with the product produced in accordance with U.S. Pat. No. 4,052,292. Thus, the present invention comprises an improvement in the process of the aforesaid U.S. patent. To this end, the entire disclosure of the said U.S. patent is incorporated herein by reference.
By "solid carbonaceous material" as employed in this disclosure and in the appended claims is meant wood, cellulose, plants, coal, peat, lignite, and similar naturally-occuring solid materials, including mixtures of these.